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Some questions-Any answers?

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Scooby_simon View Drop Down
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    Posted: 11 Feb 10 at 1:37pm

regarding gybing angles; these will be fairly deep given the sppeds these are hitting in 10kts of wind (I've heard of 30kts in 8kts true!!!)

Re tacking upwid; again I think they will be similar to "normal" beach cats; a more stategic view of sailing up wind (hence all the stuff in remote wind sensing) whereby you decide where on the course you want to be for expected shifts and wind bends instead of the more simplictic "tack on the shift when it arrives" of "quick totack boats".

IF speeds are similar, and wind is stable,  there might be some cover tacking but the stregic view of the 20 mile leg will probs override most of the time.

Mark rounding will be the same as other boats; bear-off carefully and smoothly and get the reacher up pronto!

 

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JMC_DK View Drop Down
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Post Options Post Options   Quote JMC_DK Quote  Post ReplyReply Direct Link To This Post Posted: 12 Feb 10 at 11:20am
My bet is that they will stay out of each others way and start on the same tack pretty near the middle of the line and the primary objectives will be speed + not going over the line early..  That is the closest they will be for the entire two races
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tgruitt View Drop Down
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Post Options Post Options   Quote tgruitt Quote  Post ReplyReply Direct Link To This Post Posted: 12 Feb 10 at 11:29am
Can anyone explain what a dialup is please? I'm guessing we're not talking about the type of slow internet?
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Isis View Drop Down
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Post Options Post Options   Quote Isis Quote  Post ReplyReply Direct Link To This Post Posted: 12 Feb 10 at 6:42pm
The Dialup occurs when both boats aproach on oposite tacks (as they do entering the box prestart) and turn upwind as they reach each other - Dialling down would involve turning downwind.
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Steve411 View Drop Down
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Post Options Post Options   Quote Steve411 Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 10 at 9:31am
Different subject - why is a solid sail so apparently more efficient than a conventional soft sail? (I'm thinking I should have paid more attention in physics lessons at school).
Steve B
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PeterG View Drop Down
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Post Options Post Options   Quote PeterG Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 10 at 10:00am
In large part it must be about control (though there must
also be advantages in having an airofoil whose curves
don't keep changing as the wind does). Oracle has a
series of flaps and a large number of sensors which
presumably mean that they can precisely control the shape
of different bits of the "sail" in ways that mortals with
a kicker, outhaul and cunningham can merely dream about.

Watching the start of the downwind leg yesterday what was
striking was how much more consistent Oracle's course and
heel were than Alignhi's. Partly that may be due to
Oracle being that much more powered up, but I don't mind
betting that part of it was due to the fine control they
could exercise on the wing as the wind strength
fluctuated.
Peter
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lurker View Drop Down
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Post Options Post Options   Quote lurker Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 10 at 1:27pm
A number of things change at once in the change so hard to pin the benefits of- control of twist in seven stages
double surface aerofoil (likely to improve range of efficient wind angles)
smooth & solid aerofoil (likely to be important in pointing high)
the 'slot'(likely to be especially important downwind)

at times the difference appeared big, hardly ever looked like the Cat had a gust to itself. My uneducated guess is that the slot is the crucial factor in the mix. (The idea is to prevent the airflow detaching). I wonder if a 'two part' sail could be fabricated to do similarly, maybe with straps holding the two parts.
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